Method and apparatus for co-location of two radio frequency devices

ABSTRACT

A method for avoiding signal interference between a first RF device and a second RF device is provided. The first and second RF devices are co-located and the first RF device is configured to operate within a semi-stationary range of a frequency band. The second RF device is configured to operate by changing channels within the frequency band. The method initiates with a communication interface being provided between the first RF device and the second RF device. Then, the second RF device receives the semi-stationary range and a mode for the first RF device through the communication interface. Next, the second RF device is adapted to avoid the semi-stationary range of the frequency band of the first RF device when the mode of the first RF device is in an active mode. An apparatus where two RF devices are co-located without causing interference for each other is also provided.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication No. 60/346,315 filed Dec. 28, 2001 and entitled “Co-Locationof Two RF Devices.” This provisional application is herein incorporatedby reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to wireless communicationbetween devices and more particularly to locating two radio frequency(RF) devices that share the same RF band in a common apparatus where thetwo co-located devices communicate with each other so that transmissionscan occur simultaneously without substantial interference.

Bluetooth is a short range radio technology operating in thelicense-free Industrial, Scientific and Medical (ISM) frequency bandbetween the frequencies of about 2400 Mega Hertz (MHz) to about 2483.5MHz. As originally developed, Bluetooth was to replace cables whichconnect devices such as mobile phone handsets, headsets, and portablecomputers. The promise of the Bluetooth technology has since grown toenabling wireless communications between any electrical device. Thus,the notion of a wireless personal area network (WPAN) of a 10 meterconnectivity bubble centered around the individual is developing.

At the same time, wireless local area networking (WLAN) is becomingaccepted as a wireless Ethernet solution. The protocols for WLAN's, suchas Institute of Electrical and Electronics Engineers (IEEE) 802.11boperate in the ISM frequency band as Bluetooth devices. A WLAN is anextension or replacement of wired networks for numerous computingdevices. For example, a laptop that is WLAN enabled can connect to aparticular network through an access point. Accordingly, WLAN technologyis being embraced by businesses. With Bluetooth technology directedtowards individuals and WLAN technology directed toward businesses, thetwo technologies are complementary. Therefore, a portable device, suchas a portable computer, mobile phone, personal digital assistant (PDA),etc., may contain both a WLAN RF device and a Bluetooth RF device. As aresult, the co-located RF devices must co-exist without interfering witheach other.

FIG. 1 illustrates a schematic diagram of portable computer 100containing Bluetooth RF device 102 and WLAN RF device 110 also known asInstitute of Electrical and Electronics Engineers (IEEE) standard802.11b. Bluetooth RF device 102 is in communication with antenna 104. Awireless communication pathway is established between Bluetooth RFdevice 102 and Bluetooth device 106 from antenna 104 to antenna 108.Bluetooth device 106 can be any number of electronic devices, such as aPDA, mobile phone, keyboard, mouse, speakers, etc. Portable computer 100also includes 802.11b RF device for wireless access to a local areanetwork (LAN). 802.11b RF device is in communication with antenna 112and establishes a link with access point 114 through antenna 116. Accesspoint 114 provides access to LAN 118 through an Ethernet connection.

The transmission technique used by the RF devices of FIG. 1 is a spreadspectrum technique. Two spread spectrum modulation techniques arecommonly used by devices transmitting in the ISM band. One of themodulation techniques, frequency-hopping spread spectrum (FHSS), istypically used by Bluetooth enabled devices. Under FHSS, a device cantransmit high energy in a relatively narrow band for a limited time. TheBluetooth standard uses channels of 1 MHz in width at a hop rate ofapproximately 1600 times per second. There are 79 different channelsused by the Bluetooth standard in the ISM frequency band. FHSS devices,such as Bluetooth enabled devices, are changing, i.e., hopping, channelsaccording to a mapping algorithm following a different sequencedepending on the link control state.

The second modulation technique, direct-sequence spread spectrum (DSSS),is typically used by IEEE 802.11b. Under the DSSS technique, a deviceoccupies a wider bandwidth with relatively low energy in a given segmentof the band. The DSSS technique does not hop, however, it may changefrequency bands if an access point, through which a connection is madeto a network, is changed. IEEE 802.11b uses a 22 MHz passband totransmit data. Thus, the 802.11b standard can utilize any of eleven 22MHz subchannels across the ISM frequency band.

FIG. 2 illustrates a schematic diagram of the overlap between a DSSSpassband and the Bluetooth time slots. Bluetooth is a time divisionmultiplexed (TDM) system where the basic unit of operation is a dwellperiod of 625 microseconds (μs) duration during which transmissionbetween Bluetooth devices occurs as represented by transmission slots122. DSSS packet 124 is shown overlapping three transmission slots 122.Thus, if one of the co-located RF devices of FIG. 1 which uses the FHSSmodulation technique hops to a channel that is overlapped by an activeDSSS passband from the other co-located device, then the signals willcollide. Hence, the interference caused by the collision will requirethe signals to be transmitted again, thereby degrading systemperformance. Furthermore, where a Bluetooth enabled RF device isco-located with a 802.11b RF device, the Bluetooth device is not capableof determining which frequencies in the ISM band that the 22 MHz subchannel of the 802.11b device occupies.

While attempts have been made to communicate the times to the Bluetoothdevice when the 802.11b device is actively transmitting, the systemperformance of the Bluetooth device is drastically reduced. Since theBluetooth device has no knowledge of what frequency the 802.11b deviceis using, the Bluetooth device is blocked from the entire ISM frequencyuntil the 802.11b device completes the transmission to avoid acollision. Thus, one attempt to avoid the collisions of co-locateddevices is to prevent the Bluetooth device from activity while the802.11b device is active. In another attempt to address the problem, theBluetooth device keeps track of which channels have interference througha table in memory recording good and bad transmissions and theirfrequencies. The Bluetooth device will avoid the channels wheretransmission is unsuccessful or has a high noise level based upon thepast history as represented in the table. However, since the 802.11bdevice is not always transmitting, the Bluetooth device may not capturethe frequency the 802.11b device transmits at. The Bluetooth device doesnot have the capability of actually determining which frequency the802.11b device is occupying as it is “guessing”. Therefore, when theBluetooth RF device and the 802.11b RF device are co-located, that is,in the same apparatus, such as a portable computer, the potential forinterference between them is high since the devices will be transmittingand receiving on the same frequencies from time to time. Theinterference caused from the collisions when the same frequencies areused will degrade performance for both RF devices. While theshort-comings for two co-located devices are described in terms ofBluetooth technology and 802.11b technology, they can be extended forany RF technologies co-located in the same device.

In view of the foregoing, there is a need for a method and apparatusthat allows co-located RF devices to transmit and receive simultaneouslywithout causing substantial interference with each other resulting insignal loss.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention fills this need by providing amethod and an apparatus for allowing one of the co-located radiofrequency (RF) devices to communicate the RF range in which it operatesso that the other RF device may avoid that range. The present inventionalso provides a method for the propagation of the frequency range toexternal RF devices.

In one embodiment of the present invention, a method for avoiding signalinterference between a first RF device and a second RF device isprovided. The first and second RF devices are co-located and the firstRF device is configured to operate within a semi-stationary range of afrequency band. The second RF device is configured to operate bychanging channels within the frequency band. The method initiates with acommunication interface being provided between the first RF device andthe second RF device. Then, the second RF device receives thesemi-stationary range and a mode for the first RF device through thecommunication interface. Next, the second RF device is adapted to avoidthe semi-stationary range of the frequency band of the first RF devicewhen the mode of the first RF device is in an active mode.

In another embodiment of the invention, a method for avoiding signalinterference between a first radio frequency (RF) device co-located witha second RF device is provided. The first RF device is configured tooperate within a semi-stationary range of a frequency band. The secondRF device is a slave to a third RF device. The method initiates with acommunication interface being provided between the first RF device andthe second RF device. Then, the semi-stationary range of the frequencyband for the first RF device is received through the communicationinterface at the second RF device. Next, a propagation of thesemi-stationary range through the second RF device to the third RFdevice is caused. The third RF device is adapted to avoid thesemi-stationary range of the frequency band for the first RF device inresponse to the propagation

In accordance with yet another aspect of the invention, an apparatus isprovided. The apparatus includes a first radio frequency (RF) device,the first RF device is configured to operate within a defined range of afrequency band. A second RF device is co-located with the first RFdevice. The second RF device is configured to operate by changingchannels within the frequency band. A communication interface isprovided between the first RF device and the second RF device. Thecommunication interface enables the second RF device to determine thedefined range of the frequency band that the first RF device operateswithin and a mode of the first RF device. The second RF device avoidsthe defined range of the frequency band when the second RF devicechanges channels if the first RF device is in an active mode.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute partof this specification, illustrate exemplary embodiments of the inventionand together with the description serve to explain the principles of theinvention.

FIG. 1 illustrates a schematic diagram of a portable computer containinga Bluetooth radio frequency (RF) device and a wireless local areanetwork (WLAN) RF device also known as Institute of Electrical andElectronics Engineers (IEEE) standard 802.11b RF device.

FIG. 2 illustrates a schematic diagram of the overlap between a DSSSpassband and the Bluetooth time slots.

FIG. 3 is a schematic diagram of co-located RF devices configured toavoid signal interference in accordance with one embodiment of theinvention.

FIG. 4 is a schematic diagram of a communication interface betweenco-located RF devices in accordance with one embodiment of theinvention.

FIG. 5 is a graph of frequency and time parameters to illustrate thebenefits of having the knowledge of both parameters so that interferencefrom co-located RF devices is eliminated while the bandwidth of theco-located devices is substantially maintained.

FIG. 6 is a diagram of the timing of transmitting and receiving betweenthe Bluetooth master and the Bluetooth slave under the Bluetoothprotocol.

FIG. 7 is a schematic diagram of co-located Bluetooth and 802.11b RFdevices in an apparatus where the Bluetooth device avoids the operatingfrequency of the 802.11b device and propagates the data to externalBluetooth devices in accordance with one embodiment of the invention.

FIG. 8 is a flowchart diagram of the method operations performed betweenfirst and second co-located RF devices in accordance with one embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

Several exemplary embodiments of the invention will now be described indetail with reference to the accompanying drawings. FIGS. 1 and 2 arediscussed above in the “Background of the Invention” section.

The embodiments of the present invention separates, in time andfrequency, two radio frequency (RF) signals from separate RF devicesco-located in the same apparatus. As used herein, co-located refers todevices within the same apparatus. As will be explained in more detailbelow, the frequency that one RF device is using when the RF device isin an active mode, i.e., transmitting and receiving, is communicated tothe other RF device. Thus, a master-slave relationship exists betweenthe two co-located RF devices. For illustrative purposes, theembodiments below are discussed with respect to one RF device being anInstitute of Electrical and Electronics Engineers (IEEE) 802.11b deviceand the other RF device being configured to execute the Bluetoothstandard. However, it will be apparent to one skilled in the art thatthe methods and apparatus discussed herein are can be applied to otherRF technologies, such as Ultrawideband, Zigbee, DELT and globalpositioning system (GPS).

FIG. 3 is a schematic diagram of co-located RF devices configured toavoid signal interference in accordance with one embodiment of theinvention. RF device 126 and RF device 128 are co-located in apparatus130. One skilled in the art will appreciate that RF devices 126 and 128are in communication with a central processing unit (not shown) throughbuses 134 and 136, respectively. For example, where apparatus 130 is aportable computer, RF device 126 enables a wireless local area network(WLAN) connection through the 802.11b standard and RF device 128 is aBluetooth enabled device in one embodiment of the invention. Thus, RFdevice 126 is configured to provide wireless Ethernet transmission toaccess node 136 of local area network (LAN) 138. RF device 126 is incommunication with antenna 144, while access node 136 is incommunication with antenna 148. As is well known, the antennas 144 and148 transmit and receive the radio waves that RF device 126 and 148 useto communicate with each other. One skilled in the art will appreciatethat the antennas can be any suitable antenna commercially available.Additionally, where RF device 126 executes the 802.11b standard, bus 132is any bus capable of interfacing with RF device 126, such as aperipheral component micro channel interconnect architecture (PCMCIA)bus.

Still referring to FIG. 3, where RF device 128 is a Bluetooth enableddevice, RF device 128 can communicate with an external Bluetooth enableddevice such as RF device 140. It will be apparent to one skilled in theart, that Bluetooth enabled RF device 140 may be a mouse, keyboard,personal digital assistant (PDA), mobile phone, etc. which communicateswith portable computer 130. Here, Bluetooth RF device 128 transmitsshort range RF through antenna 142 to another Bluetooth device 140,which receives the short range RF through antenna 146. Additionally,where RF device 128 is Bluetooth enabled, bus 134 is any bus capable ofinterfacing with RF device 128, such as a universal serial bus (USB).

RF device 126 and RF device 128 of FIG. 3 communicate with each otherthrough communication interface 150 in one embodiment. Communicationinterface 150 is a physical bus such as a Philips I²C bus or an IntelSystem Management (SM) bus. It should be appreciated that RF device 126and RF device 128 contain appropriate bus interfaces to enablecommunication between device 126 and 128. RF device 128 can request andreceive the frequency that RF device 126 operates at throughcommunication interface 150. Alternatively, RF device 126 and RF device128 can communicate with each other through a common central processingunit (CPU) shared by the RF devices as described below with reference toFIG. 4. In addition to requesting and receiving the operating frequencyof RF device 126, RF device 128 can request and receive a signalindicating whether RF device 126 is in an active mode throughcommunication interface 150.

FIG. 4 is a schematic diagram of a communication interface betweenco-located RF devices in accordance with one embodiment of theinvention. RF device 126 and RF device 128 are co-located in apparatus130. Continuing the example from above where apparatus 130 is a portablecomputer, RF devices 126 and 128 are in communication with CPU 151through buses 132 and 134, respectively. Where RF device 126 is an IEEE802.11b RF device, bus 132 can be any bus compatible with the IEEE802.11b device and CPU 151, such as a PCMCIA bus, a USB bus, etc. Bus132 interfaces with driver 153. It should be appreciated that bus 132transports a signal to driver 153 from RF device 126 indicating thefrequency at which the RF device is operating. In addition, a signalindicating that RF device 126 is in an active mode, i.e., transmittingor receiving, is also communicated to driver 153. Where RF device 128 isa Bluetooth enabled device, bus 134 is any bus compatible with theBluetooth device and CPU 151, such as a PCMCIA bus, a USB bus, etc. Bus134 interfaces with driver 155. Driver 155, which interfaces with bus134, includes an application programming interface (API) 159 which isconfigured to communicate requests to API 157 of driver 153.

Still referring to FIG. 4, RF device 128 sends a request to the API ofdriver 155 for the frequency the 802.11b device is operating at. Oneskilled in the art will appreciate that this request is accomplished bydriver 153 communicating with driver 155. In response to the request, afrequency range the RF device 126 is operating at is sent to driver 153through bus 132. Additionally, a signal indicating that RF device 126 isin an active mode, i.e., transmitting or receiving, may also betransmitted to driver 153 through this pathway. Thus driver 155, throughAPI 159 in communication with API 157 can access what frequency RFdevice 126 is operating at and when RF device 126 is active. As will beexplained in more detail below, where RF device 126 is an 802.11bdevice, the frequency of operation for an 802.11b device issemi-stationary. That is, the 802.11b device operates within a definedrange of the Industrial, Scientific and Medical (ISM) frequency bandthat does not change unless an access node is changed. Accordingly, RFdevice 128 can receive the information on the semi-stationary frequencyrange that RF device 126 is operating on so as to avoid thesemi-stationary frequency range to eliminate interference generated fromthe co-located devices.

FIG. 5 is a graph of frequency and time parameters to illustrate thebenefits of having the knowledge of both parameters so that interferencefrom co-located RF devices is eliminated while the bandwidth of theco-located devices is substantially maintained. The embodiment of an802.11b RF chip co-located with a Bluetooth enabled chip will be usedhere for illustrative purposes. As is well known in the art, the 802.11bstandard uses direct sequence spread spectrum (DSSS). A 22 MHz frequencyband within the ISM frequency range is used to communicate with anaccess node. This frequency band is semi-stationary, i.e., the 802.11buses this frequency for all communications as long as the communicationsare through the same access node. In other words, the semi-stationaryfrequency band will change if networks or access points are changed. Onthe other hand, the Bluetooth enabled device employs a frequency hopspread spectrum (FHSS). That is, the frequency used to transmit andreceive between Bluetooth devices in the ISM frequency range isconstantly changing or “hopping” between 79 different channels. Thesemi-stationary frequency band that the 802.11b device is operating inis represented by width 156 of bar 152. The time period that the 802.11bdevice is active is represented by bar 158. Thus, it should beappreciated that by only sending a signal to a co-located RF device,i.e., a Bluetooth device, indicating that the 802.11b device is active,will unnecessarily limit the bandwidth of the Bluetooth device. Morespecifically, the Bluetooth device does not transmit during the timethat the 802.11b device is not active, since the Bluetooth device has noknowledge of the frequency of the semi-stationary band.

However, where the Bluetooth device is configured to receive thesemi-stationary frequency band that the 802.11b device is operating inand the time period that the 802.11b device is active, as discussed withreference to FIG. 4, the bandwidth of the Bluetooth device issubstantially maintained. The intersection of bar 152 and bar 158represent the semi-stationary frequency band when the 802.11b device isactive. Thus, the Bluetooth device can avoid the semi-stationaryfrequency when the 802.11b device is active, and while the 802.11bdevice is not active, the Bluetooth device is free to “hop” in thesemi-stationary band without a performance penalty. In turn, theperformance of the Bluetooth device is substantially maintained.

It should be appreciated that the master-slave relationship fits wellwith the properties of the 802.11b protocol and the Bluetooth standard.That is, since the 802.11b device is slower moving, i.e.,semi-stationary, and does not utilize the entire ISM band at the sametime it is well suited to act as the pace setter, i.e., the master. Thefast hopping Bluetooth device which uses less bandwidth is well suitedfor the slave.

Bluetooth technology also employs a master-slave relationship whichshould not be confused with the master-slave concept described above.Where two Bluetooth devices, such as a portable computer and a PDA, arein communication with each other, the device initiating thecommunication acts as the master. Bluetooth masters set the frequencyhopping sequence while Bluetooth slaves synchronize to the master intime and frequency. A Bluetooth master can support up to seven activeBluetooth slaves.

FIG. 6 is a diagram of the timing of transmitting and receiving betweenthe Bluetooth master and the Bluetooth slave under the Bluetoothprotocol. At slot f₀ 160 the master first transmits to the slave. Here,both devices are tuned to a first radio channel. Next, the master andslave hop to the next channel, i.e., frequency, where at slot f₁ 162 theslave responds whether it understood the last transmission from themaster and is allowed to transmit any requested data to the master.Thus, the Bluetooth protocol utilizes a polled scheme where theBluetooth slave is not allowed to respond to the Bluetooth master untilthe Bluetooth slave is polled by the Bluetooth master. Moreover, theBluetooth master controls when the Bluetooth slave responds as well asthe frequency at which the response is sent.

FIG. 7 is a schematic diagram of co-located Bluetooth and 802.11b RFdevices in an apparatus where the Bluetooth device avoids the operatingfrequency of the 802.11b device and propagates the data to externalBluetooth devices in accordance with one embodiment of the invention.Bluetooth device 164 receives the semi-stationary frequency band that802.11b device 166 operates at and an active mode signal throughcommunication interface 150. As described in reference to FIG. 4,Bluetooth device 164 may alternatively receive the frequency and activemode signal through a common CPU. Bluetooth device 164 is incommunication with external Bluetooth device 168. For example, Bluetoothdevice 164 may be incorporated in a portable computer 130 while externalBluetooth device 168 may be any number of Bluetooth enabled devices,such as a PDA, mobile phone, speakers keyboard, a second portablecomputer, etc.

Still referring to FIG. 7, Bluetooth device 164 initiates communicationwith external Bluetooth device 168, therefore, Bluetooth device 164 isthe master. It should be understood that at the same time Bluetoothdevice 164 is a slave to 802.11b device as described above. Thus,Bluetooth device 164 controls the frequency at which the slave respondsand when the slave responds. The semi-stationary range that the 802.11bdevice operates at is thereby avoided in the frequency hopping ofBluetooth device 164. As Bluetooth device 168 transmissions arecontrolled as to frequency and time by Bluetooth device 164, Bluetoothdevice 168 also avoids the semi-stationary range that the 802.11b deviceoperates at. It should be appreciated that while one Bluetooth slave isillustrated in FIG. 7, up to seven slaves can be supported by aBluetooth master. Additionally, Bluetooth device 168 can be associatedwith another external Bluetooth enabled RF device

Where external Bluetooth device 168 of FIG. 7 initiates communicationwith Bluetooth device 164, Bluetooth device 168 is the master. Here, thefrequency data that 802.11b device operates at and the activity modereceived by Bluetooth device 164 via communication interface 150 ispropagated to external Bluetooth device 168. By propagating the data toBluetooth device 168, which is the master of Bluetooth device 164, thefrequency hopping algorithm for Bluetooth device 168 can be adjusted toavoid channels in the semi-stationary range used between 802.11b deviceand access node 136. If the 802.11b device should change networks, thenew semi-stationary range is propagated to external Bluetooth device168. One skilled in the art will appreciate that the Link Managerprotocol of the Bluetooth protocol stack is used to communicate thefrequency data and the activity mode received by Bluetooth device 164 toexternal Bluetooth device 168. A Link Manager protocol data unit (PDU)containing data indicating if certain channels can or can not be used issent from device 164 to external device 168. This PDU is sent wheneverthe active signal changes state. In one embodiment, the PDU may be sentindicating a de-active signal.

Propagating the channel information described above is optional due tothe performance impacts because of the restriction of what frequenciesto use. The propagation increases the performance of a IEEE 802.11b linkwhile reducing the bandwidth of the Bluetooth link when an 802.11b RFdevice and a Bluetooth RF device are co-located. Referring to FIG. 7, inone embodiment only Bluetooth device 164 is restricted from the 22 MHzsemi-stationary frequency band that the 802.11b device operates at.Here, the bandwidth between Bluetooth device 164 and external Bluetoothdevice 168 is reduced by approximately 28% (22/79) times the duty cycleof the active signal. In another embodiment, both device 164 andexternal device 168 are restricted as to what frequency to use, withdevice 164 only restricted when the 802.11b device 166 is active.Therefore, device 164 must propagate the state of the active signal toexternal device 168. Here the bandwidth of the link between theBluetooth devices is reduced by approximately 57% (22/79*2) times theduty cycle of the active signal. In yet another embodiment, externaldevice 168 is restricted all of the time irrespective of the state ofthe active signal. Device 164 does not communicate the state of theactive signal to external device 168 in this embodiment. The bandwidthbetween Bluetooth device 164 and external Bluetooth device 168 isreduced by approximately 28% (22/79) times the duty cycle of the activesignal. It should be appreciated that the reduction in bandwidthdescribed herein is applicable when co-located Bluetooth device 164 is aslave to external Bluetooth device 168.

FIG. 8 is a flowchart diagram of the method operations performed betweenfirst and second co-located RF devices in accordance with one embodimentof the invention. Here, the first RF device is configured to operatewithin a semi-stationary range of a frequency band, such as an 802.11bdevice using a DSSS as described above with reference to FIGS. 3, 5 and7. The second RF device is configured to operate by changing channelswithin the frequency band. In one embodiment, the frequency band is theISM frequency band. The method initiates with operation 170 where acommunication interface is provided between the first and second RFdevices. The communication interface may be any suitable physical bus,such as a Philips I²C bus or an Intel SM bus, between the first andsecond RF device. Alternatively, the communication interface may bethrough a common CPU as described with respect to FIG. 4. The methodthen advances to operation 172 where the semi-stationary range and amode for the first RF device is received through the communicationinterface at the second RF device. The semi-stationary range is thefrequency band that the first RF device operates at and the mode is asignal indicating whether the first RF device active, i.e., istransmitting or receiving over the semi-stationary range. Thecommunication interface enables the second RF device to receive thesemi-stationary range and the mode for the first RF device. In oneembodiment, the second RF device requests the information through thecommunication interface.

The flowchart diagram of FIG. 8 then moves to decision operation whereit is determined if the second RF device is a slave to an external RFdevice. If the second RF device is not a slave to an external RF device,then the method proceeds to operation 176 where the second RF device isadapted to avoid the semi-stationary range when the first RF device isactive. For example, the algorithm for determining the frequency hoppingof a RF device employing FHSS is adjusted to avoid the semi-stationaryrange that the first RF device uses. Furthermore, the second RF deviceonly needs to avoid the semi-stationary range when the first RF deviceis active. That is, when the mode indicates an active mode, the modifiedfrequency hopping is implemented.

If the second RF device is a slave to an external RF device, then themethod advances to operation 178 where the semi-stationary range ispropagated through the second RF device to the external device. In thecontext of Bluetooth devices, where the second RF device is a Bluetoothslave to a third RF device, i.e., a Bluetooth master, thesemi-stationary range must be propagated to the third RF device. Thus,the third RF device is adapted to avoid the semi-stationary range of thefrequency band for the first RF device as described above.

In summary, the present invention provides a method and an apparatus foravoiding signal interference for co-located RF devices. The inventionhas been described herein in terms of several exemplary embodiments.Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention. The embodiments and preferred features described above shouldbe considered exemplary, with the invention being defined by theappended claims.

With the above embodiments in mind, it should be understood that theinvention may employ various computer-implemented operations involvingdata stored in computer systems. These operations are those requiringphysical manipulation of physical quantities. Usually, though notnecessarily, these quantities take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. Further, the manipulations performed are oftenreferred to in terms, such as producing, identifying, determining, orcomparing.

Any of the operations described herein that form part of the inventionare useful machine operations. The invention also relates to a device oran apparatus for performing these operations. The apparatus may bespecially constructed for the required purposes, or it may be a generalpurpose computer selectively activated or configured by a computerprogram stored in the computer. In particular, various general purposemachines may be used with computer programs written in accordance withthe teachings herein, or it may be more convenient to construct a morespecialized apparatus to perform the required operations.

The invention can also be embodied as computer readable code on acomputer readable medium. The computer readable medium is any datastorage device that can store data which can be thereafter be read by acomputer system. Examples of the computer readable medium include harddrives, network attached storage (NAS), read-only memory, random-accessmemory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and other optical andnon-optical data storage devices. The computer readable medium can alsobe distributed over a network coupled computer systems so that thecomputer readable code is stored and executed in a distributed fashion.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

1. A method for avoiding signal interference between a first radiofrequency (RF) device and a second RF device, where the first and secondRF devices are co-located and contemporaneously active, the first RFdevice configured to operate within a semi-stationary range of afrequency band, the second RF device configured to operate by changingchannels within the frequency band, comprising: providing acommunication interface between the first RF device and the second RFdevice; receiving the semi-stationary range and a mode for the first RFdevice through the communication interface at the second RF device; andadapting the second RF device to communicate using RF signals that falloutside the semi-stationary range of the frequency band of the first RFdevice when the first RF device is in an active mode.
 2. The method ofclaim 1, further including: issuing a request from the second RF devicefor the semi-stationary range and the mode to the first RF devicethrough the communication interface.
 3. The method of claim 1, whereinthe RF devices are co-located by placement of both RF devices within asingle computer system.
 4. The method of claim 1, wherein the first RFdevice executes a 802.11b protocol and the second RF device executes aBluetooth protocol.
 5. The method of claim 1 wherein the first RF devicetransmits signals through a direct sequence spread spectrum (DSSS)modulation technique and the second RF device transmits signals througha frequency hop spread spectrum (FHSS) modulation technique.
 6. Themethod of claim 1, wherein the communication interface is a physical busbetween the first RF device and the second RF device.
 7. The method ofclaim 1, wherein the communication interface includes a centralprocessing unit common to the first RF device and the second RF device.8. A method for avoiding signal interference between a first radiofrequency (RF) device co-located with a second RF device, the first RFdevice configured to operate within a semi-stationary range of afrequency band, the second RF device being a slave to a third RF device,comprising: providing a communication interface between the first RFdevice and the second RF device; receiving the semi-stationary range ofthe frequency band for the first RF device through the communicationinterface at the second RF device; and causing a propagation of thesemi-stationary range through the second RF device to the third RFdevice, wherein the third RF device is adapted to communicate using RFsignals that fall outside the semi-stationary range of the frequencyband for the first RF device in response to the propagation.
 9. Themethod of claim 8, further including: issuing a request from the secondRF device for the semi-stationary range and the mode to the first RFdevice through the communication interface.
 10. The method of claim 8,wherein the RF devices are co-located within a computer system.
 11. Themethod of claim 8, wherein the first RF device executes a 802.11bprotocol and the second RF device executes a Bluetooth protocol.
 12. Themethod of claim 8 wherein the first RF device transmits signals througha direct sequence spread spectrum (DSSS) modulation technique and thesecond RF device transmits signals through a frequency hop spreadspectrum (FHSS) modulation technique.
 13. The method of claim 8, whereinthe communication interface is a physical bus between the first RFdevice and the second RF device.
 14. The method of claim 8, wherein thecommunication interface includes a central processing unit common to thefirst RF device and the second RF device.
 15. An apparatus comprising: afirst radio frequency (RF) device configured to operate within a definedrange of a frequency band; a second RF device co-located with the firstRF device, the second RF device configured to operate by changingchannels within the frequency band; and a communication interfacebetween the first RF device and the second RF device, the communicationinterface enabling the second RF device to determine the defined rangeof the frequency band that the first RF device operates within and amode of the first RF device, wherein the second RF device is configuredto communicate using RF signals that are outside the defined range ofthe frequency band when the second RF device changes channels if thefirst RF device is in an active mode.
 16. The apparatus of claim 15,wherein the first RF device provides wireless access to a local areanetwork.
 17. The apparatus of claim 15, wherein the second RF device isenabled to execute the Bluetooth standard.
 18. The apparatus of claim15, wherein the first RF device uses a direct sequence spread spectrummodulation technique and the second RF device uses frequency hop spreadspectrum modulation technique.
 19. The apparatus of claim 15, whereinthe communication interface is a physical bus in direct communicationwith the first RF device and the second RF device.
 20. The apparatus ofclaim 15, wherein the communication interface includes a centralprocessing unit (CPU) shared by the first and the second RF devices, thefirst RF device being in communication with the CPU through a first bus,and the second RF device being in communication with the CPU through asecond bus.
 21. The apparatus of claim 15, wherein the second RF deviceis provided with the frequency band that the first RF device operates atin response to a request from a driver associated with the second RFdevice.